Chains consisting of oval profile chain links are known in which the cross-sections of the sectional steels used, in particular on the end webs connecting the longitudinal limbs of the chain links at their ends, have a circular cross-section (US 2006/0053766 A1, DE 2007 061 512 A1).
In other known chains (DE 10 2008 034 360 A1), although the cross-sections of the end webs do not have a circular cross-section, they are formed circularly rounded on their sides facing the inner opening of the chain link in question.
In both cases, however, this has the result, when a finished chain is under tension, that the end webs in each case of two chain links engaging in one another come into contact engagement with one another on their insides, with their bearing or supporting surfaces provided there, wherein the insides of the end webs of one chain link rest against the inside of the end webs of the other chain links, arranged swivelled by 90° to them about their longitudinal axis. On such end webs, resting against one another, of in each case two chain links hooked into one another, articulation points are formed which become active when the round steel chain in question carries out a change of direction under load, for instance when running around a guide roller or during other changes of direction taking place under load. This results in the occurrence of wear at such articulation points of round steel chains under load, which can, in the end, result in the need to at least replace chain links worn out at the end webs of the articulation points, if not the need to replace the entire chain.
To produce such chains, it is known (DE 10 2007 061 512 A1), for the individual chain links, to convert corresponding profile or round steel sections into a shape corresponding to the desired chain link shape (oval, round), to hook them into one another and then connect the end faces of the pre-bent sectional steel sections to one another by welding. Since each individual chain link here has to be pre-bent into an open shape and then closed later by welding, the production of such chains is expensive.
A method of the type named at the start for producing chain links is known from DE 32 12 360 C1, in which closed chain links are hooked into open chain links and then the open chain links are closed by resistance butt welding. Used as open chain links are those chain links which consist of a U-shaped lower part and a rod-shaped upper part, wherein the ends to be welded together of the lower and upper parts of the open chain links are provided, before the welding, with substantially roof-shaped tapers, the apexes of which intersect in the welding position. As a result of this design, the conductive connection between the upper and the lower part is improved and an intensive heating in the area of the weld points is achieved, wherein small unintended shifts during assembly do not adversely affect the strength of the weld point. In this method only every second chain link is welded, whereby the manufacturing efficiency of the welding machine used is doubled compared with the known methods in which every chain link has to be welded. However, the particular design of the end faces of the U-shaped lower part as well as of the underside of the rod-shaped upper part requires an additional outlay.
The use, recommended there, of round stock on the end webs of these known chain links moreover also does not yield any improvements with respect to the life of these chain links due to joint wear.
Starting from here, the task of the invention is to improve a chain of the type named at the beginning such that the available wear volume in the joints is enlarged and thus the life of the individual chain links is increased.
In addition, the object of the invention is also to propose a method for producing such a chain which can be carried out simply and in which the production outlay is particularly low.